Latent imidazole-based curing agents are widely used as a latent curing agent in thermosetting epoxy resin compositions. However, to initiate the curing reaction, such curing agents have to be heated under pressure to 180° C. or more. Accordingly, aluminum chelating agents which allow an epoxy resin to undergo cationic polymerization are known as latent curing agents which exhibit a low-temperature rapid curing activity (Patent Document 1). Furthermore, an aluminum chelate-based latent curing agent imparted with latency by retaining such an aluminum chelating agent in a porous resin obtained by emulsion polymerization of a polyfunctional isocyanate compound has been proposed (Patent Document 2).    [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-363255    [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-70051